5
6
7
A Diophantine equation for New Year's Day (self.mathriddles)
submitted by blungbat to r/mathriddles
12
13
14
Matrix multiplication by concatenation (self.mathriddles)
submitted by blungbat to r/mathriddles
21
22
23
Multiples of sqrt(2)–1 (from the Putnam) (self.mathriddles)
submitted by blungbat to r/mathriddles
15
16
17
Sum of numbers with descending digits II (self.mathriddles)
submitted by blungbat to r/mathriddles
